Electric motors are built to a national standard, NEMA is used in North America and stands for National Electrical Manufacturers Association. Frame size reference numbers commonly range from 42 to 501 and suffix reference letters from A to Z. The codes 56C & 56J both denote frame size indication and type variation. A 56 frame size motor will have a dimension from the rotor shaft centreline to the underside of the motor feet of 3 ½” and a shaft diameter of 5/8”.

The C suffix relates to a motor with a type C face mounting and in the case of a 56C motor frame the distance from the mounting location shoulder outer face to the shaft end is 1 7/8".

The J suffix relates to a motor with a face mount for jet pumps and in the case of a 56J motor frame the distance from the mounting location shoulder outer face to the shaft end is 2 7/16". Also, the shaft end is threaded on this type.